Tunable terahertz band planar Bragg reflectors

A tunable planar narrow-band Bragg reflector based on coupling of the two propagating modes and a cutoff mode is considered. Coupled-wave analysis together with direct numerical simulations demonstrate operation of the proposed scheme up to the terahertz frequency band. Compatibility with the transportation of an intense electron beam encourages the use of a novel Bragg reflector in powerful long-pulse free electron lasers.